U.S. patent number 10,876,766 [Application Number 15/324,626] was granted by the patent office on 2020-12-29 for gas heater for water and a gas water heater.
This patent grant is currently assigned to Rheem Australia Pty Limited. The grantee listed for this patent is Rheem Australia Pty Limited. Invention is credited to Wilson Ng.
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United States Patent |
10,876,766 |
Ng |
December 29, 2020 |
Gas heater for water and a gas water heater
Abstract
The present invention provides a method of operating a gas
heater for water including the steps of: restricting a water flow
to the gas heater; determining a first rate of a first gas heating
for the restricted water flow; adjusting the gas heating to the
restricted water flow; repeating the previous steps until a heated
water has a temperature above a temperature threshold; removing the
restriction to the water flow to increase the water flow; and
determining a second rate of a second gas heating for the increased
water flow. The present invention also provides a gas water heater
which utilises such a method.
Inventors: |
Ng; Wilson (Sydney,
AU) |
Applicant: |
Name |
City |
State |
Country |
Type |
Rheem Australia Pty Limited |
Rydalmere |
N/A |
AU |
|
|
Assignee: |
Rheem Australia Pty Limited
(Rydalmere, AU)
|
Family
ID: |
1000005268925 |
Appl.
No.: |
15/324,626 |
Filed: |
May 27, 2015 |
PCT
Filed: |
May 27, 2015 |
PCT No.: |
PCT/AU2015/050279 |
371(c)(1),(2),(4) Date: |
January 06, 2017 |
PCT
Pub. No.: |
WO2016/008001 |
PCT
Pub. Date: |
January 21, 2016 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20170205115 A1 |
Jul 20, 2017 |
|
Foreign Application Priority Data
|
|
|
|
|
Jul 15, 2014 [AU] |
|
|
2014902723 |
Feb 20, 2015 [AU] |
|
|
2015900582 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F24H
1/145 (20130101); F23N 1/00 (20130101); F24H
9/2035 (20130101); F24D 19/1051 (20130101); F24D
2220/044 (20130101); F24D 2220/042 (20130101) |
Current International
Class: |
F24H
9/20 (20060101); F24H 1/14 (20060101); F24D
19/10 (20060101); F23N 1/00 (20060101) |
Field of
Search: |
;122/14.21 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
1138228 |
|
Dec 1968 |
|
GB |
|
2515768 |
|
Jan 2015 |
|
GB |
|
Other References
Canadian Office Action for corresponding Canadian application No.
2955032, dated Feb. 27, 2018. cited by applicant .
Canadian Office Action for corresponding Canadian application No.
2955032, dated Dec. 27, 2018. cited by applicant .
International Search Report and Written Opinion dated Sep. 7, 2015
for PCT/AU2015/050279. cited by applicant.
|
Primary Examiner: McAllister; Steven B
Assistant Examiner: Johnson; Benjamin W
Attorney, Agent or Firm: Troutman Pepper Hamilton Sanders
LLP
Claims
The invention claimed is:
1. A gas heater for water comprising: a gas burner; a heat
exchanger in communication with the gas burner to receive heat
therefrom; a water inlet and a water outlet coupled to the heat
exchanger, wherein the water inlet directs water into the heat
exchanger and the water outlet directs the water out from the heat
exchanger; a primary water flow path extending from the water inlet
to the water outlet through the heat exchanger; a water control
flow restrictor including a constriction and a valve, the
constriction disposed in the primary water flow path; a secondary
water flow path that bypasses the constriction and rejoins the
primary water flow path after the constriction such that water that
flows through the secondary water flow path also flows through the
heat exchanger; and a controller in operative communication with
the gas burner and the valve, wherein the controller is configured
to (a) restrict the water that flows through the secondary water
flow path by closing the valve, (b) determine a first rate of
heating of the water that flows through the heat exchanger, (c)
adjust operation of the gas burner to thereby adjust application of
the heat to the heat exchanger, (d) repeat (b)-(c) until the water
that flows out from the heat exchanger through the water outlet has
a temperature above a temperature threshold, (e) increase the water
that flows to the heat exchanger by opening the valve, and (f)
thereafter determine a second rate of heating of the water that
flows through the heat exchanger.
2. The gas heater as in claim 1, wherein the water valve is in the
secondary water flow path and is in fluid communication with the
water that flows between the water inlet and the water outlet.
3. The gas heater as in claim 1, wherein the valve is
electronically controlled.
4. The gas heater as in claim 1, wherein the first rate of heating
of the water that flows through the heat exchanger is determined
based upon at least one of a temperature of water at the water
outlet, a water flow rate, a flame on signal, a valve operating
characteristic, and a temperature of water at the water inlet.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a National Stage Entry of, and claims priority
to, PCT Patent Application No. PCT/AU2015/050279 which was filed on
27 May 2015, which claims priority to and the benefit of Australian
Patent Application No. 2015900582, which was filed on 20 Feb. 2015,
and Australian Patent Application No. 2014902723, which was filed
on 15 Jul. 2014. The entire contents and substance of the
aforementioned applications are hereby incorporated by reference in
their entireties as if fully set forth herein.
FIELD OF THE INVENTION
The present invention relates to a gas heater system, in particular
to gas heaters for producing hot water. The invention also relates
to instantaneous gas hot water systems suitable for producing hot
potable water. The invention also relates to natural aspiration
instantaneous gas water heaters as well as those with a motorised
gas flow control valve.
BACKGROUND OF THE INVENTION
There are various known apparatus and systems for gas hot water
systems as well as methods of operating gas hot water systems.
There are also gas heater systems for water which are termed
"instantaneous" to denote that the water is directly heated on
demand. That is the water is not heated earlier and then stored in
a tank for later use.
There are also natural draught gas water heaters where air for
combustion by the gas burner is supplied by a natural aspiration or
draught. That is, no fan associated with the combustion
chamber.
None of these prior art apparatus, systems and methods provides an
entirely satisfactory solution to rapidly producing hot, potable
water with a minimum of hot water delivery lag time. Nor to
minimising energy consumption when providing the hot water.
Any reference herein to known prior art does not, unless the
contrary indication appears, constitute an admission that such
prior art is commonly known by those skilled in the art to which
the invention relates, at the priority date of this
application.
SUMMARY OF THE INVENTION
The present invention aims to provide an alternative arrangement
and method gas heater for water which overcomes or ameliorates the
disadvantages of the prior art, or at least provides a useful
choice.
In one form, the invention provides a method of operating a gas
heater for water including the steps of: restricting a water flow
to the gas heater; determining a first rate of a first gas heating
for the restricted water flow; adjusting the gas heating to the
restricted water flow; repeating the previous steps until a heated
water has a temperature above a temperature threshold; removing the
restriction to the water flow to increase the water flow; and
determining a second rate of a second gas heating for the increased
water flow.
The step of removing of the restriction to the water flow includes
electronically controlling a by-pass valve to the water flow to the
gas heater.
The step of removing of the restriction to the water flow includes
using a temperature dependent shape memory alloy to actuate a
by-pass valve to the water flow to the gas heater.
The method further including the step of opening the by-pass valve
to increase the water flow.
The method further including the step of: setting at least one
temperature threshold according to a by-pass valve operating
characteristic.
The step of determining a first rate of a first gas heating rate
includes at least one of a T-outlet temperature sensed value, a
pre-heat time, a water flow rate, a flame on signal, a valve
operating characteristic and a T-inlet temperature value.
The method, whereby a hot water delivery lag time is reduced by at
least approximately 50%.
In further form, the invention provides a gas heater for water
comprising: a heat exchanger heated by a gas burner; a water inlet
and a water outlet to the heat exchanger; and a water control flow
restriction means to at least one of the water inlet and the water
outlet; wherein the water control flow restriction means increases
the water flow to the heat exchanger when a water temperature from
the water outlet is greater than a first temperature threshold.
The water flow restriction means comprises: a water flow restricted
or constricted path; and a water by-pass path; wherein the water
by-pass path is opened to increase the water flow when a water
temperature from the water outlet is greater than a first
temperature threshold.
The water by-pass path includes an electronically controlling a
by-pass valve or a temperature dependent shape memory alloy
actuated by-pass valve.
The gas heater is an instantaneous gas heater of water.
The gas heater is a natural aspiration gas heater.
The present invention also provides a gas water heater having a gas
heater operated by the method described in any one of paragraphs
[006] to [013].
The present invention further provides a gas water heater having a
gas heater as described in paragraphs [014] to [018].
The gas water heater described above can be an instantaneous gas
water heater.
The gas water heater described above can alternatively be a natural
aspiration gas water heater.
In an alternate form the invention provides a method of operating a
gas heater for water substantially as described herein with respect
to FIGS. 3a, 3b, 4 and 5.
In yet another alternate form the invention provides a gas heater
for water substantially as described herein with respect to FIGS.
1a, 1b, 1c, 1d, 2a and 2b.
In another form the invention provides a water flow restriction
means including: a water flow restricted or constricted path; and a
water by-pass path; wherein the water by-pass path is opened to
increase the water flow when a water temperature from the water
outlet is greater than a first temperature threshold.
In further form, the invention provides a method of operating a gas
heater for water including the steps of: a pre-heat operational
mode; reducing a water flow in the pre-heat mode; sensing a heated
water temperature in the pre-heat mode; increasing the water flow
when the heated water temperature is sufficient; and a normal
heating operational mode.
Further forms of the invention are as set out in the appended
claims and as apparent from the description.
BRIEF DESCRIPTION OF THE DRAWINGS
A detailed description of a preferred embodiment will follow, by
way of example only, with reference to the accompanying figures of
the drawings, in which:
FIG. 1a is a schematic of a gas heater for water with an
electronically controlled by-pass valve.
FIG. 1b is a schematic of an electrically controlled by-pass
valve.
FIGS. 1c and 1d are schematics to cross-sectional views of an
alternate electronic solenoid valve to that of FIGS. 1a and 1b.
FIG. 2a is a schematic of a gas heater for water with a shape
memory alloy mechanical water flow control device or valve.
FIG. 2b is a schematic of a shape memory alloy mechanical water
flow control device or valve.
FIGS. 3a and 3b are flowchart schematics to methods for an initial
status check of a by-pass path valve.
FIG. 4 is a flowchart schematic of a method to a pre-heat mode.
FIG. 5 is a flowchart schematic of a method to a normal temperature
control mode.
In the figures the reference numerals are prefixed by the figure
number. For example FIG. 1 is the "100" series, FIG. 2 is the "200"
series and so on.
DETAILED DESCRIPTION OF THE EMBODIMENT OR EMBODIMENTS
Traditional instantaneous gas water heaters which utilise a water
pressure differential diaphragm mechanism to control gas valve
opening are lacking in controlling of hot water temperature at
initial starting. Newer motorised gas volume flow control valves
can have a long reaction time for the motorised gas valve to adjust
its operating position, thus such water heaters may start smoothly
but it takes longer for the hot water temperature to reach the
desired set point temperature.
Both traditional instantaneous gas water heaters and the later
motorised gas valve technologies often do not require any external
electrical mains power to operate. This is an attractive feature to
users where an installation of additional power point or other
electrical supply is costly or impractical. Alternatively frequent
interruption of electrical main power supply can result in
unreliable hot water supply for gas heaters for water which are
reliant on an external electrical supply.
In adapting motorised gas volume flow control valve technology, the
problem of its inherent slow start performance reduces the
capability of fast hot water delivery and water saving. For a cool
environment/season or a cold climate, users will experience longer
waiting times for hot water. When tested to Australian standard
AS4552, a motorised gas volume flow control water heater will yield
a low energy star rating or a low energy efficiency rating for the
appliance.
Currently fully electronically controlled instantaneous gas water
heaters, which utilise mains electrical power or other external
electricity source, use a stepping motor to control water flow
volume through the water heater. Though the performance may be
adequate, such electronic control gas heaters require considerable
electrical power to compute external signals (input from various
sensors associated with the gas heater) and to control the position
of the stepping motor valve. This electrical power consumption may
be too high for the traditional battery operated instantaneous gas
water heaters to adopt.
To address this slow start behaviour to hot water delivery lag with
the use of motorised gas valve technology in traditional
instantaneous gas water heater, this invention provides a lower
energy consumption means to control water flow at cold start-up of
a gas heater for water.
An instantaneous gas water heater (hereafter termed "Water
Heater(s)") may have water pipes, water flow control devices, a
heat exchanger, sensors, ignition devices, gas flow control
devices, a gas burner and an enclosure to accommodate these
components.
The water heater 110 shown in FIG. 1a may not utilise any external
mains electrical power (240Vac and/or 110Vac for example) for its
operation. In FIG. 1a, the power module 112 which is contained by
the cabinet of the water heater can be either or a combination of
dry cell batteries, a rechargeable battery system, water turbine
electrical power generator, solar array, a Peltier electric
generator element (using the gas burner as the hot source and the
cold water inlet 140 as the cold source for example) or other
suitable self-contained or internal electricity generating
means.
When a water tap (not shown), downstream of the water heater 110 is
turned on by a user, water flows through the water pipes 114 and
the water flow sensing device 116 will generate a flow signal 118.
In the preferred embodiment, the water flow sensor 116 is a
hall-effect water flow turbine sensor. However, it can be a flow
switch or some other mechanical means to activate a limit switch.
Once a flow signal 118 is provided by the water flow sensor 116,
the power module 112 will power an ignition module 120, a
temperature controller 122 and a gas valve 124 to initiate a gas
ignition cycle.
When a flame signal is provided via a flame sensor 126 or
thermocouple (depending on the ignition system design), gas flow to
the gas burner 113 will be maintained to heat up water that passes
through the heat exchanger 128 in a natural draught combustion
chamber 130.
The temperature of the hot water is monitored by a temperature
sensor 132 near the exit of the hot water outlet 134. The
temperature sensor 132 can be a NTC thermistor. A temperature
signal 136 produced by the temperature sensor 132 is a feedback to
the temperature controller 122. In the preferred embodiment, the
temperature controller 122 is an electronic circuit with firmware
which is designed to: accept power from the power module 112, to
accept signals 118, 136 from the water flow sensor 116 and the
temperature sensor 132; to condition these input signals, and then
to output an electrical signal for gas flow 138 to control the
position of the motorised gas volume flow control valve 124. The
objective is to achieve a stable outlet hot water temperature at
the hot water outlet 134 which matches a pre-set temperature at the
temperature controller from start-up at a low fluid flow-rate to a
higher fluid flow-rate after the start-up period or
start-up/pre-heat operational mode.
The invention includes the methods and means to control water flow
during the gas heater ignition process when the temperature
(T-outlet) of the outlet 134 water is cool (below a 1st temperature
threshold, T1). The methods and means to control water flow can be
achieved by an electronic actuation and control means of the
preferred embodiment shown in FIGS. 1a, 1b, 1c and 1d described in
detail further below. An alternate embodiment to a mechanical means
is shown in FIGS. 2a and 2b, as described in detail further
below.
FIGS. 3a to 5 are flowcharts to the method of controlling and/or
restricting water flow so as to reduce hot water delivery lag and
improve "instantaneous" provision of hot water on demand. The
flowcharts of FIGS. 3a to 5 schematically show the method used for
the apparatus embodiments of FIGS. 1a, 1b, 1c, 1d, 2a and 2b. The
process variables used in the flowcharts and detailed in the
description below are listed as follows:
T-inlet: a temperature of the water at the cold water inlet
140;
T-outlet: a temperature of the water at the hot water outlet 134 as
sensed by the temperature sensor 132 which provides a temperature
signal 136;
Fm: a water flow rate through the main line 148, 156, 248 or
constricted/restricted path of the valve or flow control device
142, 152, 212, in FIGS. 1b, 1c, 1d and 2b when a water tap is
turned on;
Fb: a water flow rate through either of the respective by-pass
paths 144, 154, 220 of either of the by-pass valves 142, 152, 212
of FIGS. 1b, 1c, 1d and 2b;
Ftot: a water flow rate through the water pipes 114 and heat
exchanger 128 of the gas heater; Ftot=Fb+Fm; T1: a first
temperature threshold applied to T-outlet. Below this temperature
T1 the by-pass paths 144, 154, 220 of the valves 142, 152, 212 are
closed. Also below this temperature the gas heater operates in a
pre-heat mode; T2: a second temperature threshold applied to
T-outlet. Above the T2 temperature the by-pass paths 144, 154, 220
are open for respective by-pass valves 142, 152, 212 and the gas
heater operates in the normal temperature control mode; the setting
of the T1 and T2 temperature thresholds is dependent on a
particular valve type's operating characteristic. This is described
in detail with respect to FIGS. 1a to 1d and FIGS. 2a and 2b. For
example the shape memory alloy (SMA) valve 212 of FIG. 2b may begin
opening as the temperature rises above T1 and be fully open at
temperature T2; and T3: a temperature set point for the desired hot
water temperature from the hot water outlet when the gas heater is
operating in the normal temperature control mode. A Preferred
Apparatus Embodiment--Electronically Controlled Water Flow By-Pass
Valve 142:
FIG. 1a depicts a water by-pass valve 142 in the inlet water flow
path to the heat exchanger 128. FIG. 1b shows an enlarged and more
detailed schematic of the water by-pass valve 142. The control of
water flow (Fb) through the by-pass path 144 is achieved by
activating via a valve signal line 145 a solenoid valve 146. As
shown in FIGS. 1a and 1b, this water by-pass valve 142 is located
near the cold water inlet 140 of the water heater 110. However, the
valve 142 can be located along any convenient point of the water
flow path of the fluid pipes 114; for example near the hot water
outlet 134, along the fluid pipes 114 to and from the heat
exchanger 128 or can be integrated with the housing of the
temperature sensor 132.
When a water tap is turned on by the user which is sufficient
enough to be detected by the water flow sensor 116, an ignition
sequence will start. A flow rate "Fm" through the main line 148 of
the valve 142 is provided by a constriction 150 in the main line
148 when the water tap is turned on. The constriction 150 and
cross-sectional area "A0" of the main line 148 of the valve 142 is
described further below.
At substantially the same time as when the water tap being turned
on is sensed the water temperature T-outlet detected by the
temperature sensor 132. It will be readily appreciated that an
additional, optional temperature sensor can be installed at the
cold water inlet 140 of the water heater to provide a further
temperature signal from the inlet 140. The cold water inlet
temperature, T-inlet, may be used to provide additional input to
the determination or calculation of the gas heating rates as
described in detail with respect to in FIGS. 4 and 5.
If the hot water outlet water temperature T-outlet (or cold water
inlet temperature T-inlet, if fitted to the water heater) is lower
than the first threshold temperature, T1, then a temperature
controller 122 will command 145 the water bypass valve 142 to shut
off water flow going through a by-pass path 144, thus Fb.apprxeq.0
L/min (where Fb is the flow rate through the by-pass path 144 shown
in the valve of FIG. 1b). The by-pass path 144 may also be
described as a secondary water flow path and a method of
restricting the water flow. By shutting off part of the water flow
path of by-pass path 144, it results in a higher water flow
resistance in the water circuit 114. At the same inlet water
pressure, the water flow rate will be reduced in the water
circuit/water flow path 114 to the flow rate of Fm through only the
main line 148 of the valve 142, that is Ftot=Fm.
Upon successful ignition of the main gas burner 113 and Fb
remaining substantially zero in the water by-pass path 144, the
water heater 110 operates in a pre-heat mode. With a reduced water
flow rate of Fm only passing through the heat exchanger 128, the
water in the heat exchanger gains heat faster at a given input gas
rate, thus raising water temperature quicker. The heated water at
the hot water outlet 134 is measured by the temperature sensor 132
and which provides a signal 136 feedback for T-outlet to the
temperature controller 122. The rate of heating in the pre-heat
mode can be controlled by the gas input rate. The pre-heat mode
method is described further with respect to the flowchart of FIG.
4. The method to the initial status of the by-pass path 144 is
described further with respect to the flowchart of FIG. 3.
The pre-heat mode is maintained until hot water temperature
T-outlet at the outlet 134 reaches a 2nd temperature threshold T2.
T2 can be set between 32.degree. C. to 40.degree. C. and is
dependent on the pre-set temperature point T3 and the thermal mass
of the heat exchanger. When hot water temperature T-outlet is above
the 2nd threshold temperature T2, the temperature controller 122
will command via valve activation signal line 145 the by-pass path
144 to re-open. The water heater 110 now operates in a normal
temperature control mode so as to thermostatically control hot
water temperature to its pre-set temperature point T3. The water
flow rate through the gas heater is now Ftot=Fm+Fb, where
Fb.noteq.0. T2 can be the same as T3 but usually T2 is set at a
lower temperature than T3. This is because in the pre-heat mode,
the ratio of gas input rate to water flow volume is higher than the
normal temperature control mode. That is, at pre-heat mode,
depending on the construction and design of the heat exchanger 128,
a full gas input to water flow rate ratio may be approximately
doubled for example as compared to its normal input capacity for
the normal temperature control method.
At the end of the pre-heat mode, a considerable amount of heat
energy is stored in heat exchanger 128. By turning on the by-pass
path 144 before hot water temperature reaches set point temperature
T3, the extra volume of water flowing in the heat exchanger 128 can
prevent overheating of the heat exchanger 128 and temperature
overshoot at the hot water outlet 134.
The normal temperature control mode method is described further
with respect to the flowchart of FIG. 5.
As described above and with respect to FIGS. 3a to 5, the method of
controlling water flow during the pre-heat mode includes shutting
off a water by-pass path 144. It will be readily appreciated that
the water by-pass path does not necessarily have to be fully sealed
or closed. A small leakage can still occur with satisfactory
operation of the pre-heat mode.
In addition to or alternatively to controlling a by-pass path Fb:
reduced water flow at pre-heat mode can be achieved by the
constriction 150 of FIG. 1b controlling or further restricting a
water flow cross-sectional area (A0) of the main line 148 through
the valve 142. That is controlling the cross-sectional area A0 to
Fm as shown in FIGS. 1b, 1c and 1d in addition to or as an
alternative to the by-pass valve and path 144. Such fine tuning of
the restriction area for the Fm flow-rate is also described further
below with respect to FIGS. 1c and 1d.
When an operating water heater is turned off by closing a water tap
downstream of the outlet 134, residual heat energy may maintain an
elevated temperature of the water stored inside the water heater
for a considerable time period; that is losses of heat to the
ambient environment may be gradual. For example the exchanger 128
and gas burner 113 may stay hot for a period after water flow
stops. As long as the water temperature measured at the temperature
sensor 132 remains higher than the 1st temperature threshold T1,
the bypass path 142 valve will remain open. The preheat mode will
not be activated when the by-pass path valve is open and
T-outlet.gtoreq.T1. This is because the water heater may retain
sufficient residual heat to achieve a fast heat up cycle with the
normal temperature control mode method operating between
temperatures T1 and T3.
It will be readily appreciated that the first temperature threshold
T1 may be substantially the same as the second temperature
threshold T2 for the electronically controlled valve 142, 152.
It will also be readily appreciated that for the electronically
controlled valve 142, 152 the temperature threshold decision point
settings are: when T-outlet<T1 then close bypass path 144, 154,
otherwise the bypass path remains open. In pre-heat mode, the T2
temperature threshold is the point to re-open the bypass path 144,
154.
FIGS. 1c and 1d are schematics to cross-sectional views of an
alternate electronic solenoid valve 152. FIG. 1c is a longitudinal
cross-section through the water pipe 114 into and out of the
alternate solenoid valve 152 and also a longitudinal cross-section
through a valve spindle 158 of the alternate valve 152. The valve
152 is shown open with a valve plug 160 away from a valve seat 162.
In dashed lines the valve plug 160'' is shown in the closed
position against the valve seat 162. The alternate solenoid valve
152 also has an electrically operated solenoid 164 which actuates
the spindle 158 against the return spring 166 in order to open the
valve 152 by pulling away the valve plug 160 from the valve seat
162.
Opening the valve 152 opens the bypass path 154 to provide the
additional fluid flow rate Fb as shown in FIG. 1c, such that
Ftot=Fb+Fm. The closed position of the alternate valve 152 with the
valve plug 160 against the valve seat 162 closes the bypass path
such that Fb.apprxeq.0. In the closed position water may only flow
through the valve 152 via the channels/restricted path 156 shown in
FIG. 1c. Thus the total fluid flow rate Ftot=Fm only for the closed
position or state of the alternate valve 152.
FIG. 1d is a cross sectional view along the lines 1-1 of FIG. 1c to
show a plan view of the valve seat 162. The valve seat face has
recessed channels 156 through which water may flow when the valve
152 is closed. Fm may be varied by varying the number of channels
156 and/or the cross-sectional of each channel/restriction 156 in
the face of the valve seat 162. FIG. 1d shows four channels or
restrictions 156.
An Alternate Apparatus Embodiment--SMA (Shape-Memory-Alloy)
Mechanical Water Flow Control Device:
As an alternative to the electronic control means described with
respect to of FIGS. 1a to 1d, a Shape Memory Alloy (SMA) flow
control device 212 is installed near the hot water outlet 134 of
the water heater or at any convenient point in the water flow path
114 downstream of the heat exchanger 128; where a water temperature
change is appropriate to control the actions of the SMA valve 212.
FIGS. 2a and 2b are schematics of the mechanical water flow control
device 212 and the gas heater 210 for water.
The SMA valve 212 is designed in such a way that the SMA material
214 always sits in the main water flow path from the heat exchanger
128 and so directly detecting the temperature of the water as shown
in FIG. 2b. The SMA material changes its physical property (shape
or length for example) as a known function to temperature range.
This temperature dependent characteristic is utilised to control
the movement of valve 216 position in the valve seat 218. This
temperature dependent characteristic of the SMA valve may also be
termed a valve operating characteristic. As the water heater 210 is
started from cold and then heated up, it then causes a reaction of
the SMA material to adjust water flow with the valve.
At idle or cold start, the water temperature at the hot water
outlet 134 may be substantially the same as that of the cold water
inlet 140. The SMA operated by-pass path 220 will be shut off or
closed at low ambient temperature threshold T1. When a water tap
downstream of the water heater 210 is turned on, it starts with a
reduced water flow volume or flow rate Fm because of the increased
flow resistance from the constriction in the main line 248 of the
mechanical flow control device 212. That is Ftot=Fm and
Fb.apprxeq.0 L/min.
The water heater 210 then goes through ignition sequence and
pre-heat mode as described earlier with respect to FIG. 1a and
further with respect to the flowchart of FIG. 4.
Because of the thermal inertia of the SMA material 214, its
reaction time to temperature changes may be considerably longer
than the electronic system described with respect to preferred
embodiment of FIGS. 1a to 1d. When the outlet temperature 134
T-outlet reaches the 2nd threshold T2 (in this case T2 may be set
at a temperature lower than that in preferred embodiment, to
compensate for the slower reaction/response time of the SMA valve),
it relies on the SMA material 214 to react and slowly increase the
flow to the by-pass path 220 in accordance with the SMA valve
operating characteristic with fluid temperature. Gas input will be
quickly reduced at this point T2 to compensate the reaction time in
order to avoid overheating and temperature overshoot at the hot
water outlet 134.
The operating characteristic SMA valve is accommodated for by the
T1 threshold being the temperature below which the SMA valve is
fully closed. The T2 threshold is the temperature above which the
SMA valve is fully open. Between T1 and T2 the SMA valve is
partially open. The pre-heat mode may still operate below and up to
T2. The normal temperature control mode may operate from above T2
and including T3.
As the water temperature increases, the SMA by-pass path 220 will
reach its fully open position so that Ftot=Fm+Fb, where Fb.noteq.0.
At the stage of the fully open position of the valve 216 & 218
the water heater 210 operates in a normal temperature and fluid
flow rate control mode as also described with respect to the
flowchart of FIG. 5.
When the water heater 210 is then turned off at the water tap
downstream, the residual heat remaining in the system may allow the
bypass path 220 to stay open if the water temperature about the SMA
material is above the second temperature threshold T2. Therefore,
there is no water flow throttling when the water heater is warm at
above T2.
It will be readily appreciated that there is an art to the
understanding of the desired characteristic and reaction time of
the SMA material 214, and determination or selection of a 1st
threshold temperature T1, the 2nd threshold temperature T2 and the
set point temperature T3, dictates the control of gas input rate
required in the pre-heat mode. That is the sensing and control by
the temperature controller 122. Similarly it will also be readily
be appreciated that there is an art to the understanding of the
valve operating characteristic with respect to the SMA material
used here in one valve in comparison to the valve operating
characteristic of the electrically actuated valve of FIGS. 1a to
1d.
Alternatively instead of using a by-pass path, the SMA valve can be
designed to solely control the opening of the main water flow path
114 (not shown). That is an alternative SMA valve (not shown) may
operate between a partially open state and a fully open state for
fluid flow control with no by-pass path 144. That is the
alternative SMA valve only restricts the water flow within the gas
heater fluid flow path.
Both the preferred embodiment and the alternate embodiment as
described herein to this invention provides a means and a method to
momentarily or temporarily reduce or restrict water flow rate
during a cold start-up of a water heater with the pre-heat mode.
The effect of adopting either of these methods or apparatuses
reduces hot water delivery lag time, usually from approximately 25
seconds down to approximately 15 seconds. That is the hot water
delivery lag time may be reduced by approximately 50%. In addition
appreciably warm water can be delivered in the first approximately
5 to 15 seconds of the pre-heat mode. As a result, gas energy
consumed to heat the initial volume of water at cold start to a set
temperature is reduced. The energy usage may be maximised compare
to similar water heaters without these devices and methods as
described above.
The flowcharts of FIGS. 3a, 3b, 4 and 5 are described further as
follows. The dashed lines in the flowcharts of FIGS. 3a to 5
indicate functions, features, inputs and the like which are
optional.
FIG. 3a is a flowchart schematic of a method to an initial status
check of by-pass path 144, 220 for the electronic control by-pass
valve 142 and the mechanical water flow control device 212. The
by-pass valves 142, 212 of FIGS. 1b and 2b operate as normally open
valves with respective fluid by-pass path 144, 220. The by-pass
path opens and closes depending on the T-outlet temperature of the
water for delivery to the hot water outlet 134 and the respective
temperature thresholds T1 and T2 as well as the valve operating
characteristics previously described. The opening of the by-pass
path increases the water flow as described earlier in accordance
with Ftotal=Fm+Fb.
The initial status check of the by-pass valve state may be started
310 either at tap turn on via the flow sensing for the
electronically controlled by-pass valve 142 of FIGS. 1a to 1d or
continuously for the SMA by-pass valve 212 of FIGS. 2a and 2b.
T-outlet is then compared 312 against the T1 or T2 thresholds
depending on the valve operating characteristic 314.
As described above the by-pass path is closed 316 if for an
electronically controlled valve the T-outlet temperature is less
than T1. If an SMA valve is used then the pass path is fully closed
if T-outlet temperature is less than T1. The gas heater then
proceeds 302 to the pre-heat mode method of FIG. 4.
If T-outlet temperature is above the T1 threshold applicable to a
valve operating characteristic then the by-pass path may be opened
318 so that the water flow rate is Ftot=Fm+Fb, where Fb.noteq.0.
The gas heater may then proceed 304 to the normal control mode
method of FIG. 5.
Optionally as shown in FIG. 3b the water flow may also be sensed
320 as sufficient for the normal temperature control mode method of
FIG. 5. If for example a hot water tap is only turned on
sufficiently open for satisfactory operation of the normal
temperature control method then the water flow sensing of 320 may
be unnecessary and omitted from the method as shown in FIG. 3a.
However if the hot water tap may only be turned on partially which
is insufficient for safe operation of the heat exchanger 128 then
gas heater may not proceed to the normal temperature control method
and may instead default to another safe operating mode version (not
shown).
Also optionally the steps to sensing T-outlet 312 and opening the
by-pass path 318 may be repeated if the gas heater is cooling down
and there is insufficient water flow for normal operation as shown
in FIG. 3b. The repetition may be delayed by a cool down time
constant 322 which is characteristic of the gas heater and the
valve operating characteristic. For example a gas heater with a
larger thermal inertia will have a larger cool down time constant,
so successive repeats may be delayed further.
FIG. 4 is a flowchart schematic of a method to a pre-heat mode as
described above. The pre-heat method begins 302 from the by-pass
being closed as described above and the methods of FIGS. 3a and 3b.
The water flow rate is then sensed 410 as being sufficient, for
example at the flow rate of Fm. If the flow rate is not sufficient
then continuous monitoring 412 to when the flow rate is sufficient
may be done. When the water flow rate is sufficient the gas heater
may proceed to determining a first gas heating rate 414 for the gas
burner to heat the heat exchanger 128. In determining the first gas
heating rate of the heat exchanger, the T-outlet temperature sensed
value 416 and the desired pre-heat time 418 may be used. The
pre-heat time 418 may derived from the hot water delivery lag time
for the invention and changed as suitable for a particular gas
heater apparatus and the desired hot water delivery lag time. Other
optional data values that may also be used to additionally
determine the first gas heating rate 414 are: a water flow rate
420, a flame on signal 422, a valve operating characteristic 314
and a T-inlet temperature value 424.
The optional T-inlet sensed temperature at the cold water inlet 140
may be used to provide an additional temperature data input T-inlet
424 to determine the first gas heating rate 414 as applied by the
gas volume flow control valve 124 and gas burner 113. For example
in the winter season the temperature of the water from the cold
water inlet 140 may be significantly cooler than the water supply
temperature in the summer season. Accordingly the cooler water in
the winter season will require more heating by the gas burner 113
to bring it to the desired or set temperature for the hot water at
the hot water outlet 134 with minimal hot water delivery lag.
Once the gas heating rate has been determined 414 the gas heater
may proceed to adjusting 426 a first gas heating to the heat
exchanger. Then the gas heater may proceed to comparing 428 the
T-outlet temperature to the second temperature threshold T2. If
T-outlet is less than T2 then the gas heater remains in pre-heat
mode with another determination 414 or continuous determination 414
of the necessary gas heating rate in pre-heat mode.
If the T-outlet is greater than T2 then the gas heater proceeds to
opening 318 the by-pass valve and then proceeding 402 to the normal
temperature control mode as described above and with respect to the
flowchart of FIG. 5.
FIG. 5 is a flowchart schematic of a method to a normal temperature
control mode as described above. The normal temperature control
mode may be started from the pre-heat mode 402 or from an already
warm 304 gas heater at a temperature above T2 or T1 as described
above. A second gas heating rate may be determined 510 with data
inputs such as the T3 desired hot water temperature set point value
512 and the T-outlet temperature value 416. Further optional data
value inputs for further determining the second gas heating rate
510 may be the second temperature threshold T2 value 514, the flame
on signal 422, T-inlet temperature value 424, the valve operating
characteristics 314 and the flow rate 420.
Once the second gas heating rate has been determined 510 a second
gas heating rate to the heat exchanger may be adjusted 516. Whilst
the normal temperature control mode is in operation the
determination 510 of second gas heating rate and subsequent
adjustment 516 of second gas heating may be continued in order to
maintain the hot water temperature substantially as desired, for
example approximately to the T3 temperature set point.
It will be readily appreciated that additional control and method
steps may be added to FIG. 5 for such safety conditions as when
water flow stops or reduces to unsatisfactory flow rates, when
there is no flame signal and the like.
Further advantages to those described above are: maximise gas
energy efficiency, reduce hot water delivery lag time. Other
advantages are: more immediate hot water which heats intervening
pipe work at the low fluid flow rate Fm. Overall faster hot water
supply to a shower head or a tap than other systems or apparatus.
Also, there is a no electricity supply option; that is the gas
heater for water is suitable for an independent electrical supply
within the gas heater itself.
In this specification, terms denoting direction, such as vertical,
up, down, left, right etc. or rotation, should be taken to refer to
the directions or rotations relative to the corresponding drawing
rather than to absolute directions or rotations unless the context
require otherwise.
Where ever it is used, the word "comprising" is to be understood in
its "open" sense, that is, in the sense of "including", and thus
not limited to its "closed" sense, that is the sense of "consisting
only of". A corresponding meaning is to be attributed to the
corresponding words "comprise", "comprised" and "comprises" where
they appear.
It will be understood that the invention disclosed and defined
herein extends to all alternative combinations of two or more of
the individual features mentioned or evident from the text. All of
these different combinations constitute various alternative aspects
of the invention.
While particular embodiments of this invention have been described,
it will be evident to those skilled in the art that the present
invention may be embodied in other specific forms without departing
from the essential characteristics thereof. The present embodiments
and examples are therefore to be considered in all respects as
illustrative and not restrictive, and all modifications which would
be obvious to those skilled in the art are therefore intended to be
embraced therein.
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